1. Field of the Invention
The present invention relates to a rear vehicle detecting apparatus, and more particularly to a rear vehicle detecting apparatus of a vehicle which can detect another vehicle following the vehicle from oblique rear in the same direction as the vehicle runs.
2. Description of the Related Art
Generally, a vehicle such as an automobile runs on a lane indicated on a road, and the driver of the vehicle changes the lane into an adjacent lane based on the running situation. In a case to change the running lane, the driver confirms whether or not another vehicle is running on the adjacent lane, by a rearview mirror such as a door mirror, a room mirror and a fender mirror, and then the driver changes the running lane.
Conventionally, the technique is proposed, in which a transmission and reception unit for laser light or millimeter wave is arranged in the front portion of a following vehicle, and the running speed of the following vehicle is decelerated based on an output signal from the transmission and reception unit, when the distance from the following vehicle to a preceding vehicle is smaller than a predetermined value.
According to this proposal, when the preceding vehicle and the following vehicle runs on the same lane, the laser from the following vehicle is reflected in the rear of the preceding vehicle, because the rear of the preceding vehicle and the front of the following vehicle oppose. Therefore, it is possible for the reflected laser to be detected by the reception unit arranged in the front of the following vehicle.
However, when the preceding vehicle and the following vehicle are running on different lanes, the laser beam reflected by the preceding vehicle can not be sufficiently detected by the reception unit of the following vehicle, because the rear of the preceding vehicle and the front of the following vehicle do not oppose. Therefore, the detection precision of the existence of the preceding vehicle reduces remarkably.